Water-soluble unit dose articles are known. Such articles often comprise compositions intended to be released into an aqueous liquid upon addition of the article to the aqueous liquid. Normally the article is manufactured such that the composition is contained within a compartment formed from a water-soluble film. Upon addition to water, the film dissolves and releases the composition. Consumers find such articles both convenient and efficient for a range of applications.
The articles are manufactured by forming a water-soluble film in a mould to the desired shape. Rectangular or square shapes are often used as these maximize the volume available for the composition. However, when the film is formed into square or rectangular shaped moulds, areas of weakness, or increased stress, are formed into the corners due to over-stretching of the film. These areas of weakness are prone to forming pinholes, ripping or splitting during manufacture, packing, shipping, or other general handling, causing failure of the article. These areas of weakness form regardless of whether the corners are rounded or are formed from sharp angles.
Articles manufactured to have a circular shape overcome the article structural integrity issue, however have the downside of reduced internal volume available for the composition for a given amount of film material used during manufacture of the product using conventional methods. The internal volume can be smaller than wanted for a particular application. Altering the footprint of the pouch results in increased film material usage which results in higher costs. When the diameter of the mold is increased to compensate for volume lost for the circle-shaped mould, fewer mold cavities will fit across the width of a manufacturing line and consequently fewer articles will be produced.
Furthermore, circular shaped pouches result in complexity during manufacture. During manufacture, film is formed into the relevant 3D shape in order to make the pouch. Often a first film and a second film are used to make the pouch, said films being sealed together at a seal area. Conventional unit dose article making methods involve the use of moulds which comprise a matrix of multiple rows and columns of mould cavities. Each cavity is used to form a separate article once cut and separated from a web of unit dose articles made. Once sealed and cut from the web of unit dose articles produced, excess film material can then be cut away from the edges of the article. If the seal area is circular, this adds complexity to the cutting operation. Alternatively, the seal area may be cut into a square or rectangular shape, which removes a degree of manufacturing complexity, however, this results in wasted film material in the case where the seal area itself is circular in shape. This wasted film material negatively increases the overall dissolution time of the pouch (especially when it is considered that the wasted material consists of two films sealed together so also represents the ‘thickest’ part of the film material) and also has a negative impact on the aesthetic qualities of the pouch.
Therefore, there is a need in the art for a water-soluble unit dose article that maximizes internal volume whilst still maintaining excellent structural stability (especially avoiding corners) and dissolution speed.
The Inventors surprisingly found that a water-soluble unit dose article having a substantially super-elliptical shape met this need.